Double hung window



Jan. 23, 1940. s. MADSEN DOUBLE HUNG WINDOW Filed Sept. 50, 193'? m 9 r m8 .M. 7 W. H msws wwmy P z M u m H W Z 55 f mm w m w 5 Morzze J I 0 s .m MU QJQM m1 5 i 0 1 60020006 /095 .m. m d 96 LL Q 000 21%:

Patented Jan. 23, 1940 UNITED "STATES DOUBLE nuns wnmow Sci-n Madsen, Clinton, rows, llSlIIlor to Curtis Companies Incorporated, Clinton, Iowa, a corporation of Iowa 8 Application September 30,1931. Serial No. 166,638

5 Claims.

An object of my invention is to provide in a double hung type of window employing spring means for counter balancing the sashes thereof and combination weather strip and friction means, a method of using not only the springs but also the weather strip construction as a means to govern the resultant counter-balancing friction and to provide, if necessary, additional friction area beyond those offered by the usual weather strips.

A further object is to provide the combined weather stripping and friction means in the form of coacting members of resilient rust-proof metal providing frictional coaction between the edges of the sash and the window frame.

A further object is to provide part of the friction means in theform of guide channels serving as liners for grooves in the window frame along the edgesof the sash, these liners receiving the weather strip elements and having the terminal edges of their flanges bent outwardly to cover the face of the window framev adjacent the edges of the sash whereby such faces'need not be painted and accordingly the desired clearance between the window frame and the edge of the sash is constantly maintained and the possibility of paint getting into the groove for the weather stripping is eliminated, and therefore the coefiicient of friction between the sliding elements of the window is not interfered with. I

A further object is to provide in a window structure, means whereby the friction needed for the counterbalancing springs may be standardized, it being possible to increase the degree of friction as when necessary with heavier sashes by increasing the friction area, for instance by extending the stiles of the sash beyond the rails thereof, thus permitting longer weather strip members to be used'and also providing for extra length of spring and less travel of the sash in order to reduce the total build upof the tension of the spring.

Still another object is to provide a structure which makes it possible to utilize a simple means a of spring calculation for eliminating thede'pendence on a trial method to secure the proper spring for a given window sash.

Still another object is to provide a window structure which can be economically manufactured, the various features of design and possibility of precalculation ,for the necessary springs for a given window contributing to economy of manufacture yet making the apparatus adaptable to all sizes and styles of double hung windows.

With these and other objects in view, my invention consists in the arrangement and combi nation of the various parts of my double hung window, whereby the objects contemplated are attained, as hereinafter more fully set forth,

pointed out in my claims, and illustrated in the accompanying drawing, in which:

Figure 1 is an inside elevation of a double hung window structure embodying my invention.

Figure 2 is an enlarged sectional view on the line 2--2 of Figure 1, showing the counter-balance springs and weather strip connections.

Figure 3 is a vertical sectional view on the line 3-3 of Figure 2, showing the counter-balance spring for the upper sash. I

Figure 4 is a sectional view on the line 4-4 of Figure 2, showing the counter-balance spring for the lower sash.

Figure 5 is an enlarged sectional view on the line 5-5 of Figure 1 showing weather stripping at the sill of the window.

Figure 6 is an inside elevation of a window structure showing only the upper sash and its suspension, this sash being of the circle top type.

Figure 7 is a portion of a chart which I use to determinethe weight of a given sash as a step in a method of calculating the proper counterbalance spring to be used for a given sash.

Figure 8 is a curve chart of lifting capacities of different springs to determine the proper one to'use.

Figure'9 is a calculation data sheet which I use to compile the necessary data for a given sash and check up on whether or not the spring calculations have been correctly made; and

Figure 10 is a sectional view of the weather strip showing a modified form of friction means to retain the sash in various adjusted positions.

On the accompanying drawing I have used the reference numeral 10 to indicate a side jamb for a window frame for double hung sashes. The upper sash is indicated generally at US and the lower sash at LS. The sashes US and LS are vertically slidable. They are illustrated as being made of wood, but obviously could be made of iron or other metal if desired.

For counter-balancing the sashes US and LS I provide counter-balance springs II and i2. For each sash there is a spring for each side edge thereof. To accommodate the springs. and I2, the sashes are rabbeted along their outer I and inner corners respectively as indicated at l3 and I4 and the jamb I0 is grooved as at l5 and Hi. The blind stop I] of the window frame is rabbeted as at l8 to reduce the-necessary size of the rabbet I3 and likewise the inside stop It is rabbeted at 20.

As shown best in Figures 3 and 4, the upper ends of the springs Ii and i2 are secured to the jamb It) as by being hooked over screws 2| and 22 respectively. Their lower ends are secured to the lower edges of the sashes by means of hooks 23 and 24 respectively. When counter-balance springs are used as illustrated, it is desirable in order to reduce and standardize the frictional 00 engagement between the sashes and the window frame to provide sashes of such size that there is considerable play between their side edges and the side lamb of the window frame. This is clearly illustrated in Figure 2 by spacing between the elements US, l0 and i1 and between the elements LS, i0 and I9. Such spacing, however, permits considerable infiltration of air and in order to minimize such infiltration, weather strips are desirable.

With respect to the characteristics of the springs II and i2, it is desirable that they approximately counter-balance the weight of the sash at its mid travel for a purpose which will hereinafter be explained. Obviously, therefore, when the sash is either above or below mid travel, some means should be used to retain it in such position without the necessity of having to provide fastening hardware for this purpose. Since it is desirable to weather strip the window, I use the weather stripping as a friction means for this purpose.

With the foregoing requirements in mind, I have provided weather strips WS, for instance in the form of Y-shaped members of rust-proof resilient sheet metal. These are partially received in grooves 25 along the side edges of the sashes, the legs of the Y-shaped weather strip members being received in somewhat narrow sub-grooves 2B. The weather strips WS may be retained in position as by screws 21.

The arms of the Y-shaped weather strips extend into grooves 28 of the side jamb iii. The grooves 28 are lined with channel-shaped liner elements 29 made preferably of rust-proof sheet metal. The terminal edges of the flanges of the elements 29 are bent outwardly at right angles as indicated at 30.

The arms of the weather strip WS are initially formed wider than the channel-shaped elements 29 so that when placed in assembled position, they provide considerable friction to resist movement of the sash and resiliently engage the sides of the channel-shaped elements 29 throughout the extent of the weather strips so as to provide a weather tight joint. The central portions of the arms of the weather strips are: bowed slightly toward each other to permit slight inward and outward shifting of the sashes relative to the window frame without disturbing the weather tight joint between the weather strips and the channel-shaped elements.

The portions 3a and 4a. of Figures 3 and 4, respectively, are sections through the channelshaped elements 29 and through the weather strip grooves 25 and 26 just ahead of the weather strips WS.

For the sill of the window I provide a weather strip connection which is shown in Figure 5. The sill is indicated at 3!. The lower sash LS has a groove 32 in the bottom edge thereof which receives a ribbed portion 33 of a weather strip WS'. The weather strip has a pair of diverging wings 34 inclined downwardly toward the window sill and which resiliently engage the window sill when the lower sash is closed,, thus effectively sealing the sash throughout its width at the sill against infiltration of air and water.

The weather strip WS may' be retained in position as by nails or the like 35 extending through the ribbed portion 33 thereof and into the sash L8.

The foregoing description gives a general outline of my window structure. To economically manufacture a window structure of the kind described, there are several problems which must be overcome. I take care of such problems by the design of my window structure, the purpose of the various features of which will now be pointed out.

With respect to the channel-shaped member 28, the flanges 30 form a very important function. These flanges, being metal, need not be painted or otherwise flnished by the painter when finishing the other parts of the window. Where these flanges are eliminated and the faces of the side jambs adjacent the edges of the sasl'i'es painted there are two objections.

First, a painted surface is presented to the edge of the sash, and second, there is serious danger of getting paint into the channel members thereby interfering with the operation of the weather strips and undesirably modifying the frictional engagement thereof which should be in a. desired proportion to the tension of the counter-balance springs.

By providing the flanges 30, it is unnecessaryto paint the faces of the jamb next to the edges of the sashes and accordingly there is no reduction in clearance by paint coats and likewise no possibility of gumming the adjacent surfaces with paint. Metal sliding faces are provided by the flanges 30 which contributes to easy sliding of the sashes. It is possible that the painter may get some paint on these faces, but that is 30 not so serious as getting paint into the channelshaped elements 28. The flanges 30 therefore make it unnecessary for the painter to get his brush close to the groove for the weather strip, thus entirely eliminating the likelihood of getting paint into the grooves.

The flanges 30 also insure straighter walls for the side flanges 29 of the channel-shaped elements 28 as they reinforce them against any undesired distortion. This gives a more uniform frictional coaction between the weather strips and the channel-shaped elements during adjustrnent of the sash. Accordingly, the window structure can be assembled with assurance that there will be predetermined friction per unit length of weather strip and therefore the desired friction to resist movement of the sash due to the bias of the counter-balance springs can be accurately predetermined.

Another problem confronting the manufacturer of a spring balanced double hung window is the problem of how to compensate for the change in spring tension when the spring is extended to different lengths due to the different positions of the sash relative to the window frame. There must be sumcient friction in the weather strip connections to retain the sash in any desired position other than mid travel as in other positions the springs do not exactly balance the sash. It is desirable, however, that the spring exert an actual lift about equal to the Weight of the sash to provide easy sash movement up and down. Logically, therefore, the spring should balance the weight of the sash at mid travel.

Although other types of springs have been used, I prefer to use an extension spring which in its contracted position with the sash up, is still under tension to partially counter-balance the sash. Such spring will operate friction free when the channel provided for it as shown in Figure 2 is sufficiently large to avoid rubbing of the spring against the walls thereof.

Since the spring balances the weight of the sash at mid travel, it is obvious that when in raised the sash when the sash is down), the sash will stay down. Conversely, if the friction is greater than the weight of the sash (lessened by the lift of the springs when the sash is up), the sash will stay up. The friction,-however, should not greatly exceed the lift or weight as it is desirable to make the sash slide as easily as possible. Therefore, if a system of charts, curves and data sheets is used, such as I illustrate'in Figures 7, 8 and 9, it is possible to predetermine the proper spring for a given sash without guess work or the necessity of a trial method. Where the friction of a given weather strip is insufflclent, it is obvious that various methods may be used to increase the friction such as spreading the arms of the weather strip. This, however, is unsatisfactory because it is indeterminate. Also a uniform friction per unit length might be secured by different designs or shapes of weather strips. With respect to efliciency in the manufacturing process, however, it. is desirable to use, as far as possible, a standardized section of weather stripping and then vary the friction area, for instance by varying the length of the weather strip to secure a different degree of friction as desired. Accordingly, I provide sashes in which the friction of the weather strip may be increased by increasing the length of the weather strip.

Ordinarily the weather strip would extend the height of the sash. On the upper sash, however, I provide downward extensions 36 and the weather strip for the upper sash may extend along this extension to a position indicated at 31 (see Figure 3). Likewise the lower sash may have an upwardly directed extension 38 permitting the weather strip to extend to a position indicated at 39 (see Figure 4). The extensions 36 and 38 accomplish three purposes. First, they permit an increase in the degree of friction that may be needed for a counter-balance spring, and second, they shorten the possible travel of the sash, thus shortening the distance of the extension of the spring-between minimum and maximum and reducing the total build up of the tension of the spring and third, they lengthen the stile of the sash so that longer, more resilient springs may be used to secure a wider range of sash balance for a given spring.

The extensions 36 are particularly desirable in connection with a circle topwindow as shown in Figure 6, wherein the extensions are indicated at 36a and the upper sash is indicated at US.

. Due to the semi-circular form of the top of the window frame, the counter-balance springs Ila must be hooked at their upper ends a considerable distance below the upper end of the window frame. The extensions 36a can thus be made relatively long so as to both reduce the travel of the sash and increase the available length of the spring for a circle top window. The same effect may of coursebe obtained in any other suitable way, for instance, by providing additional coacting friction means between the movable parts of the window. As an example, for providing additional friction area beyond that provided by the usual weather strip extending from top to bottom of the sash where, for constructional or architectural reasons, I cannot use the extensions 36 and 33 I may use additional friction elements, such as the one illustrated at 40 in Figure 10. The element 40 has a pair of wings frictionally engaging the inner faces of a somewhat deeper channel element 290.. This provides additional friction, the degree of which may be controlled by using various lengths of the element 40. By this means the friction area can be substantially doubled over that provided by the usual weather strip or can be predetermined to any value between that of the usual weather strip and double the weather strip length.

I will now explain the method by which astandardized weather strip unit and a series or group of standardized springs of different lifting capacities and lengths are used to balance a large range of sashes. It is of utmost importance to use standardized parts in mass production to effect economy of manufacture and it is equally important to know beforehand just what springs may be required to balance any particular sash. As a starting point, the chart in Figure 7 gives the weight in pounds of a sash having a glass of certain width and height. For instance, a sash having a 30 x 18 glass weighs 9 pounds. Referring to Figure 9, a calculation or. data sheet is shown wherein the glass size is entered-in column I and its weight in column 2. Columns 3, 4 and can be filled in, column 3 indicating the length of the spring when the sash is up, column 5 when it is down and column 4 when it is midway between up and down.

The next column to command consideration is column 9 wherein the pounds of friction of the weather strip are to be filled in.

The particular weather strip illustrated has been found in actual practice most eflicient when it exerts one pound of friction for each seven inches of contact length.

The weather strip length being known and the unit friction per length being known, the friction in pounds can be filled in. With a glass 18 inches high, the sash is approximately 21 inches high and the friction being one pound per seven inches, it is obvious that the total length of the weather strip on the two sides of the sash being 42 inches, the weather strip friction will be six pounds.

We now know that a spring should be selected which will lift close to nine pounds when the sash is at mid travel. The mid travel extension of the spring is twenty-eight and one-half inches. Referring now to the curve chart in Figure 8, the horizontal line for a spring having a nine pound lift crosses the, twenty-eight and one-half inch vertical line at the point marked X. Spring curves for springs of 12, 14, 16 and 18 inches in length appear on the chart and the point X comes closest to the line for the fourteen inch spring.

Accordingly the fourteen inch spring is the one which would come most nearly to meeting the requirements. The spring curves, of course, are predetermined by tests of actual springs and when once the springs are stocked, it is then merely necessary to use the one predetermined according to. the chart of Figure 8.

In column 10 of Figure 9, the fourteen inch spring is then entered. The chart of Figure 8 is now used to fill in columns 6, I and 8 of Figure 9. The fourteen inch spring when stretched to nineteen inches or the"up position of the sash, will exert a lift of six pounds. Likewise at mid position the spring lifts 9.7 pounds, while in the down" position of the sash, when the spring is extended to thirty-eight inches, its lift will be 13.4 pounds.

The next step in the process is to check as to whether or not the spring selected will fill the requirements. The lift of the spring at mid position (column 'I, Figure 9) is slightly more than nine pounds. This is generally satisfactory and preferred. If it should be too great, the connection of the spring to the lamb can be lowered as by placing the screws 2| or 22 at a lower elevation. To determine whether or not the sash will stay up, the spring lifts six pounds (column 6) at the "up" position of the sash and the friction of the weather strip being six pounds, the

total is twelve pounds. As the sash weighs only nine pounds, there is a three pound leeway. This is satisfactory for a light weight sash such as the one used in the foregoing example as excess friction is negligible where there is not much weight of the sash to overcome by the person operating the window.

To determine whetherthe sash will stay down, its weight plus the friction amounts to fifteen pounds. The spring lift at the lower position of the sash is 13.4 pounds (column 8). Thus the weight plus the friction exceeds by 1.6 pounds the lift of the spring and, therefore, the sash will stay down. When larger and heavier sashes are used, thr margin of excess friction reduces. This is as it should be because the less extra friction experienced with a large sash, the more nearly minimum will be the necessary expenditure of energy in adjusting the sash.

Where the height of the sash is insufficient to permit use of a weather strip of sufficient length and thereby sufficient friction to overcome the lift of the spring when the sash is lowered or the weight of the sash when it is raised, the extensions 36 and 38 may be employed to give both additional friction and additional length of spring. The additional length of spring reduces the change in tension in the spring from minimum to maximum position and also reduces such difference in the tension due to the extensions 36 and 38 reducing the travel of the sash. Therefore the extensions serve a very important function in connection with spring hung sashes.

The tables and charts shown in Figures 7, 8 and 9 eliminate dependence on a trial method of seiection of the springs as the design of any new window structure can be based on calculated values. The use of the system of calculation permits the use of standardized sets of springs. The structure illustrated permits the use of standardized weather strip sections with fixed and predetermined tension. A wider range of sash construction is possible because the calculations can be based on the full use of the spring and weather strip range. Predetermination of the workability of a window to be built is an important consideration of a manufacturer and is a special asset for economical manufacture of the window disclosed.

-The weather strip WS' shown in Figure 5 provides an effective double seal against the weather along the sill of the window. The wings 34, when the sash is closed, are under tension to snugly engage the sill throughout the length of the Weather strip regardless of slight irregularities of the contour of the sill.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope.

I claim as my invention:

1. For use with a window structure comprising a window frame, sashes vertically slidable therein. counter-balance springs therefor and weather strip connections between the sides of said window frame and said sashes serving as combined guide and friction elements and providing uniform friction per unit area; means for increasing the total friction to hold said sashes against movement due to the bias of said springs, said means comprising extensions of said weather stripsbeyond the normal height of the sashes. said weather strips and extensions being carried by said sashes.

2. For use with a window structure comprising a window frame, sashes vertically slidable therein, counter-balance springs therefor and weather strip connections between the sides of said window frame and said sashes serving as combined guide and friction means and providing uniform friction per unit area; such area being adjustable in size by modification of the construction of the weather strips and the weather strips of any selected size being carried by the sashes.

3. For use with a. window structure having counter-balance means for the sash thereof comprising springs and weather strips carried by said sash and providing friction to hold said sash, said weather strips providing uniform friction during full travel of the sash; means to adjust the contact length of said weather strips to provide the necessary friction to retain the sash against sliding due to the action of the spring when the sash is at opposite limits of its travel and to provide slight additional friction to insure the sash remaining in such position yet permitting movement of the sash with a minimum of effort.

4. For use with a window structure having a window frame, a sash therein, balancing springs to lift the sash and substantially balance it at mid travel, and weather strip means carried by said sash to serve the dual purpose of sealing the sash against infiltration of air and to provide friction to retain the sash against movement; additional friction means comprising elongation of said weather strip means beyond the normal height of said sash to retain said sash in position, said springs being of such size that the build-up rate of tension of the springs is never greater during one-half the travel of the sash than the combined friction of the weather strip and said additional friction means.

5. For use with a window structure having balancing and weather stripping means, said balancing means comprising springs acting to lift the sash and said weather stripping means being carried by the sash and including parts which frictionally engage each other to resist movement of the sash; said weather stripping means extending beyond the normal height of the sash to increase the degree of frictional engagement, said weather stripping means together with its extension providing friction which is constant after installation and slightly in excess of the change in spring tension during one-half the travel of the sash.

' SERN MADSEN. 

